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    Estrus Synchronization of Beef and Dairy Cows

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    Author
    Fish, Ronald Dean
    Issue Date
    2011
    Keywords
    progesterone
    Animal Sciences
    CIDR
    Estrus synchronization
    Advisor
    Marchello, John A.
    
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    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Abstract
    An estrus synchronization trial was conducted to determine the efficacy of adding an injection of gonadotropin releasing hormone (GnRH) at initiation of the controlled intravaginal drug releasing device (CIDR®) progesterone synchronization protocol in heifers. Nulliparous (n=121) beef heifers were randomly assigned to one of two treatment groups. All heifers received a CIDR® implant at the initiation of the breeding season. Half of the heifers (Select Synch) received an injection of GnRH. Heifers in the Select Synch treatment group had a lower numerical response (76.7% versus 88.3%) to treatment (detected in heat) and an overall lower artificial conception rate (46.0% versus 53.3%), but no statistical difference was detected. Days to conception and artificial insemination conception rates for both groups were similar for all heifers inseminated. Three hundred multiparous Hereford, crossbred and composite beef cows were assigned to one of two breeding groups (Early and Late) based on calving date and randomly assigned to receive an injection of GnRH at the time of CIDR® insertion (Select Synch). The addition of GnRH did not impact the percentage of cows detected in estrus or days to conception. Conception rates were not affected by the addition of GnRH (Select Synch), however cows in the early breeding group were more likely to become pregnant (58% versus 45%) by artificial insemination (P<0.02). An experiment evaluated the efficacy of the CIDR® protocol to synchronize estrus in Arizona Holstein dairy cows (n=696). Cows assigned to the CIDR® protocol (n=337) received a CIDR® insert at the end of the voluntary waiting period (55 days). CIDR®s were removed and an injection of prostaglandin was administered seven days after insertion. There was no difference due to CIDR® treatment in number of services per conception or first service conception rate. CIDR® treatment reduced days to first service, days open at first service, and days open (P<0.02). Warm season had a deleterious effect on number of services, days to first service, first service conception rate and days open (P<0.0001). In summary, estrus synchronization improved postpartum reproductive performance; however, thermal stress continues to be a major barrier to reproductive efficiency.
    Type
    text
    Electronic Dissertation
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Graduate College
    Animal Sciences
    Degree Grantor
    University of Arizona
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